Fibrous insert for reinforcing foam plastic products and process for the production of these foam plastic products

ABSTRACT

CRASH PADS OR THE LIKE ESSENTIALLY COMPOSED OF A POLYMERIC FOAM MATERIAL AND RANDOMLY DISPOSED THERETHROUGH A NONWOVEN FABRIC OF SUBSTANTIALLY CONTINOUS FILAMENTS.

June 18, 1974 P. HOPPE EIAL 3,817,819 FIBROUS INSERT FOR REINFORCINGFDA! PLASTIC PRODUCTS AND PROCESS FOR THE IRODUOTION OF THESE FOAMPLASTIC PRODUCTS Filed Nov. 26, 1971 FIG. I. FIG. 2.

FIG. 5A. FIG. 5B.

United States Patent 3,817,819 FIBROUS INSERT FOR REINFORCING FOAMPLASTIC PRODUCTS AND PROCESS FOR THE PRODUCTION OF THESE FOAM PLAS- TICPRODUCTS Peter Hoppe, Troisdorf, Gustav Drouveu, Bensberg Moltzfeld, andJohann Muller, Leverkusen, Germany, assignors to BayerAktiengesellschaft, Leverkusen, Germany Continuation-in-part ofabandoned application Ser. No. 853,425, Aug. 27, 1969. This applicationNov. 26, 1971, Ser. No. 202,197 Claims priority, application Germany,Oct. 18, 1968, P 18 03 790.6 Int. Cl. 1332b 3/14 U.S. Cl. 161-140 2Claims ABSTRACT OF THE DISCLOSURE Crash pads or the like essentiallycomposed of a polymeric foam material and randomly disposed therethrougha nonwoven fabric of substantially continuous filaments.

This application is a continuation in part of Application Ser. No.853,425 filed Aug. 27, 1969, now abandoned.

This invention relates to foam form articles. It more particularlyrefers to such articles which are used as crash pads or other structureshaving shock absorbing, foam-form components.

It is known to utilize foam-form shaped articles, such as polyurethanefoam articles of appropriate shape, as crash pads for automobile dashboards and the like. It is also known to utilize such foam-formmaterials in structures where the foam is a core which is covered byother rigid or flexible materials such as sheet metal, solid plastic,fiber reinforced plastic, ply woods etc. Such foams as form crash padsgenerally have densities of about 100 to 800 *kgJmF, while such foams asare used in sandwich construction are more generally rigid and have adensity of about 60 to 100 kgjmfi.

Where flexible foams are used, they tend to absorb input shock by meansof their resiliency and compression. Rigid foams however break, uponbeing subjected to input compression shock, in a brittle manner andtherefore have the capacity to absorb very little if any shock.

It is known to reinforce foam-form articles as well as non-foam formplastic articles by incorporating reinforcing fibers or filamentstherein. This type of reinforcing is conventionally used to improve thetensile strength properties of such plastic materials. It is known toproduce these fiber reinforced plastics by admixing the fibers with amoldable plastic and then molding the admixture, or by forming a threedimensional fiber structure corresponding generally to the shape of thefinal desired product and then foaming the plastic through theinterstices at the fibrous preform. It has been the practice to makethese fibrous preforms of a multiplicity of very short fibers, usuallyglass fibers, of about 5 to cm. in length.

Such fibrous preforms were made by relatively conventional non-wovenfabric production techniques in which the fibers are formed, in ageometrically random distribution and orientation, into an appropriatesize and shape; and are then bonded together in this size and shape toan extent sufiicicnt to stabilize them in this size and shape.

After the plastic foaming process was carried out, the final reinforcedfoam plastic product had a high bulk density of about 750 to 900 kg./m.However, these products suflered from the distinct disadvantage that theindividual fibers had very little effect upon the tensile strength ofthe product because of their rather short length. Further, it wasimpossible or at least substantially impossible to produce very bulkyproducts of lower density, by foaming in situ, that is products havingratios of all three dimensions to each other of about 1:1:1 with athickness of at least 3 cm. to about 5:5 :1.

Further, it has been found that foam-form plastics of relatively highbulk reinforced with a fibrous structure composed of short or stablelength fibers showed a shiver or vibration effect when subjected tosudden compressive forces (shock) which is quite undesirable in a crashpad or other shock absorbing device.

It is therefore an important object of this invention to provide a novelfiber reinforced, bulky foam plastic structure which is more readilycapable of absorbing crash type of shock than have similar articles inthe past.

Another object of this invention is to provide a more resilient and moredimensionally stable foam form material than has been available in thepast.

Other and additional objects of this invention will become apparent froma consideration of this entire specification including the claims anddrawing hereof.

When considering this invention, one must understand that the productionof a fiber reinforced foam articles of high bulk is to be distinguishedfrom the production of a relatively thin film or sheet form article.Neither are the same problems encountered nor are the same solutions tothese problems applicable. The high bulk articles to which the instantinvention is directed are those whose overall dimensions are at least ina ratio of about l:l:l to l00:l00:1 to l00:l00:20 with a thickness of atleast 30 cm.

In accord with and fulfilling these objects, one aspect of thisinvention lies in the production of a bulky shaped article by forming anon-woven fabric of substantially continuous filaments generallycorresponding to the shape and size of the final article desired;bonding this bulky nonwoven fabric of continuous filaments togetherpredominantly at the intersection of crossing filaments or portionsthereof to an extent at least sufficient to stabilize the bulkystructure and give is sufiicient dimensional stability to stand up to itbeing impregnated with and enveloped in plastic foam withoutsignificantly varying its dimensions; and foaming a plastic material in,through and around the continuous filament preform, and within asuitable shaped molding means to form the finished bulky, filamentreinforced plastic foam product.

Understanding of this invention will be facilitated by reference to theaccompanying drawing in which:

FIG. 1 is a photograph of an unreinforced foam test article after havingbeen subjected to a crash test;

FIG. 2 is a photographic of a foam article reinforced with filamentsaccording to this invention after having been subjected to a crash test;

FIG. 3 is similar to FIG. 2 but showing a sandwich or composite article;

FIG. 4 is similar to FIG. 2 but showing a foam body reinforced withshort fibers;

FIG. 5a is a power-distance relation curve recording the deformation ofan article as shown in FIG. 3; and FIEICI. 5b is similar to FIG. 5a butfor the article of By endless filaments are meant filaments which are aslong as the processing techniques and the size of the fibrous insertproduced therefrom allow. Such filaments are normally obtained in theproduction of fibres and are available commercially. It may be assumed,however, that an endless filament has a length of at least metres. It isto be understood, of course, that the filaments may also be produceddirectly from the melt as endless filaments by means of a spinneret stepbefore formation of the fibrous insert.

The thickness of the filaments is of the order of 5 to 100 denier,depending on the intended use to which the filaments are to be put andthe stresses to which they will be subjected. If several endlessfilaments are to be used together, one may, of course, use filaments ofdifferent thicknesses and/or of different materials. To improve the bondbetween the filaments and foam plastic, it is advisable to use not onlythose filaments with a smooth surface but also those with a structuredsurface.

The percentage by weight of filaments in proportion to the total weightof the finished reinforced foam plastic may vary between 5% and 50%depending on the purpose and the chosen bulk density of the foamplastic.

Inorganic materials suitable for the filaments are, for example, metal,carbon or glass. Polyamide, polyacrylonitrile, acetyl cellulose,polyesters or their combinations are suitable examples of organicmaterials of which the filaments of this invention are made. The foamsystems may be liquid, expansible systems based on unsaturated polyesterresins, epoxy resins, phenol formaldehyde resins, polyurethanes, rubberbased natural or synthetic latices, etc. Furthermore, any liquidexpansible foam forming systems which yield semihard or hard foams maybe used.

It is often necessary for the plastic reinforced foam bodies to havelocal variations in the bulk density according to the different purposesfor which they are intended. The invention therefore provides for aspecial embodiment in which the fibrous inserts also differ locally intheir density and bulk according to the bulk density required. The foamfinally produced will then have greater strength at these points.Moreover, mechanical binding elements or complete section reinforcementsof metal, polymer materials or wood may be embedded in the fibrousinsert and the foam may then be expanded through this.

The fibrous insert may be produced, e.g. as a continuous web, forexample on a conveyor band and afterwards be cut up into individualpieces of the required size. One particular application lies inproducing the fibrous insert as a preformed article, if necessary, ofcomplicated three-dimensional structure for the reinforced foam productwhich is to be produced. This is carried out in a compression mould orsuction mould conforming to the contour of the final foam product.

The purpose for the production of such foam product using the fibrousinsert according to the invention is based on the fact that fibres arewetted with binder in known manner and then deposited, preferably as apreformed insert, through which a foamable liquid chemical is thenfoamed. The inventive feature of this process is that the fibrous insertis formed from one or more endless filaments by three-dimensionaldeposition. The advantages already mentioned above are achieved by thismeans because the endless filament or filaments are fixed by the binderat their intersecting points of contact.

The deposition may, for example, be crosswise and/or in the form of aspiral or irregularly. This deposition may be carried out automatically,both the supply of the filament and its deposition being carried outeither individually or coupled.

Compared with the known process, the process according to the inventionalso has the special advantage that the operation of breaking up endlessfibres into short fibres is eliminated.

According to a particular embodiment of the process of the invention,the filaments are deposited with localized differences in density.According to the invention, this is achieved either by producing therequired density by localized and/or intermittent application of asuitable, if necessary, additional, partial vacuum to the fibrous insertwhich is being formed. The partial vacuum is moreover preferablyvariable in time and place during the process of deposition. The fibrousinsert is thus sucked to the surface on which it is supported, and thesubsequent filaments deposited on it form a more or less loose and bulkypackage. Alternatively, the invention provides for localized and/ortemporary variation of the number of endless filaments used for formingthe fibrous insert. In this special case, one may also use in additionshorter filaments than those described above. According to anotheradvantageous method of carrying out the process for obtaining localizeddifferences in the density of deposition of the endless filaments, theinvention provides for the variation in place and/ or time of the titreof endless filaments supplied. This is achieved, for example, bysubjecting the finished filaments to a cold or hot stretching or, in thecase of filaments drawn from the melt, these are subjected to stretchingwhich varies with time. The variation in titre depends both on the typeof filament material and on the required mechanical properties of thefibrous insert at the particular points of the insert.

The process provides another especially advantageous embodiment in whichthe finished fibrous insert is precompressed at least at certain pointsThis can be effected, for example, by pressing the fibrous insertbetween two plates so that it is fixed by heat. If only certain pointsof the fibrous insert are to be compressed, the plates may beappropriately contoured. The precompression may be effected by thefoaming mould itself immediately before the foaming process.

What is claimed is:

1. A bulky shaped article having an overall dimension ratio of at leastabout 1:1:1 to :100:1 to 100:100:20 with the last value in the ratiobeing the thickness, with a thickness of at least 30 cm., consistingessentially of a mass of geometrically disarrayed continuous filaments,which form a bulky mass of filaments, which filaments are bondedtogether at crossing points thereof with a binder, said filaments havinga denier between 5 and 100 and a length of at least 100 meters, whichmass has substantially the same size and shape as said article, andfoam-form plastic material in the interstices of and about said filamentmass.

2. A bulky shaped article according to claim 1 wherein said foam-formplastic material is a liquid, expansible system based on a memberselected from the group consisting of unsaturated polyester resins,epoxy resins, phenol-formaldehyde resins, polyurethanes, natural rubberbased latices and synthetic rubber based latices, said filaments beingpresent between 5 and 50% based upon the total weight of the finishedbulky shaped article.

References Cited UNITED STATES PATENTS 3,686,048 8/1972 Sehirtzinger156-161 3,669,566 6/1972 Bourquardez l61-144 3,627,603 12/ 1971 Greig264--47 X 3,591,444 7/ 1971 Hoppe 264-257 2,972,554 2/1961 Muskat 264-47X 3,382,302 5/ 1968 Marzocchi 264257 3,028,284 4/1962 Reeves 2642573,546,060 12/1970 Hoppe et al 264-47 X 3,617,594 6/1969 Willy 264-47 X3,025,202 3/1962 Morgan 264-47 GEORGE F. LESMES, Primary Examiner M. B.WITTENBERG, Assistant Examiner US. Cl. X.R.

